1. Field of the Invention
This invention relates to a motor comprising a stator where a lubricated bearing is fitted in a bearing holder; and a rotor where a rotation shaft is rotatably supported by the bearing, an oil deflector is provided on one end portion of the rotation shaft in order to return lubricant oil back to the bearing, the lubricant oil having leaked from the bearing to the one end portion of the rotation shaft, and a hub is fixedly attached to the rotation shaft so as to oppose the oil deflector, thereby preventing the lubricant oil from reaching the hub even when the oil leaks from the bearing and reaches the oil deflector.
2. Description of the Related Art
Generally, a motor is composed of a stator stationarily mounted therein and a rotor rotatably driven in relation to the stator.
The above-mentioned stator includes a motor base stationarily mounted therein, a bearing holder attached on the motor base, a bearing fitted in the bearing holder, a stator core and a plural of coils wound around the stator core.
On the other hand, the afore-mentioned rotor is composed of a rotation shaft rotatably supported by the bearing, a hub fixedly attached on one end portion of the rotation shaft, a rotor yoke rotatable in unison with the hub and a magnet fixedly attached on the rotor yoke.
The plural of coils wound around the stator core of the stator oppose the magnet provided in the hub via the rotor yoke, with a slight gap allocated therebetween. The motor composed as above operate in such a way that a magnetic force is generated between the stator coil and the magnet when the stator coil provided for each phase is energized, so as to rotate the hub integrally with the rotation shaft.
By the way, the hub can be provided with a polygon mirror, a hard disc, an optical disc or the like.
As the bearing for rotatably supporting the rotation shaft, there is used a lubricated bearing such as an oil-impregnated sintered bearing, a fluid pressure bearing, a ball bearing or the like. Among the motors using such a bearing, there is disclosed for example in Japanese Patent Application Laid-open Publication No. 2001-61253 (pages 3 to 4, and FIG. 2) a motor designed to prevent a reduction of lubricant oil in an oil-impregnated sintered bearing.
FIG. 1 is a magnified vertical cross-sectional view of the oil-impregnated sintered bearing in the related art motor, the oil-impregnated sintered bearing supporting rotatably a rotation shaft.
A related art motor 100 shown in FIG. 1 is disclosed in the aforementioned publication (No. 2001-61253) and will be explained briefly here referring thereto.
In the related art motor 100 shown in FIG. 1, a stator portion S has a bearing holder 102 mounted on a motor base 101. The bearing holder 102 has a center hole 102 into which an oil-impregnated sintered bearing 104 impregnated with oil 103 is fitted by pressure-fitting or a like method. The oil-impregnated sintered bearing 104 is cylindrically shaped and has a center hole 104a penetrating the center portion thereof. In addition, the oil-impregnated sintered bearing 104 has a first circular concave portion 104b on the top and a second circular concave portion 104c on the bottom, the concave portions 104b, 104c being open in a shape of circular concave.
On the other hand in a rotor R, there is supported rotatably a rotation shaft 105 in the center hole 104a of the oil-impregnated sintered bearing 104 as follows. On one end portion (an upper end portion) of the rotation shaft 105, a first rotation body (equivalently, a first oil deflector) 106 and a hub 107 are fixedly attached by pressure-fitting or a like method so that the hub 107 tightly contacts the first rotation body 106. On the other end (a lower end) of the rotation shaft 105, a second rotation body (equivalently, a second oil deflector) 108 is fitted into the center hole 104a, the second rotation body 108 being composed of a cut-washer. The rotation shaft 105 is inserted into the center hole 104a of the oil-impregnated sintered bearing 104 until the tip of the other end abuts a thrust plate 109 attached on the motor base 101.
The first and the second rotation body (respectively equivalent to the first and the second oil deflector) 106, 108, which are provided respectively on the one portion and the other end of the rotation shaft 105, are positioned in the first and the second circular concave portion 104b, 104c respectively provided in the upper and the lower portion of the oil-impregnated sintered bearing 104. The oil 103, even if leaked from the oil-impregnated sintered bearing 104, can be splattered by the first and the second rotation body 106, 108 into the first and the second circular concave portion 104b, 104c, thereby preventing a reduction of the oil impregnated in the bearing 104.
Although the related art motor 100 can prevent a reduction of an oil amount in the oil-impregnated sintered bearing 104 by attaching the first and the second rotation body (respectively equivalent to the first and the second oil deflector) 106, 108 on the one portion and the other end of the rotation shaft 105, part of the oil 103 that has leaked from the oil-impregnated sintered bearing 104 may leak farther to the hub 107 via the first rotation body 106.
The reason why this happens will be described in the following. The first rotation body (equivalent to the first oil deflector) 106 pressure-fitted to the one end (the upper end) portion of the rotation shaft 105 as a center hole 106a; and the hub 107 has also a center hole 107a Regarding these center holes 106a, 107b, it is rather impossible to realize a perfectly precise diameter and circularity. Therefore, when the first rotation body 106 is pressure-fitted to the one end of the rotation shaft 105 and then the hub 107 is pressure-fitted on the first rotation body 106, the center hole 106a of the first rotation body 106 and the center hole 107a of the hub 107 may deform to easily cause clearance between these holes 106a, 107a and the rotation shaft 105. Under these circumstances, since the first rotation body 106 and the hub 107 tightly contact each other, the oil 103 that has leaked upward from the oil-impregnated sintered bearing 104 can come above the upper surface (not shown) of the hub 107 passing through the clearance due to capillary phenomenon.
In addition, some (or, a slight) amount of the oil 103 leaked from the oil-impregnated sintered bearing 104 can flow along the circumferential surface of the first rotation body 106 to reach the lower surface of the hub 107 that is tightly fixed to the first rotation body 106 and then to reach the upper surface (not shown) of the hub 107 through the center hole 107a of the hub 107.
The oil 103 that has reached the upper surface (not shown) of the hub 107 spreads thereon by centrifugal force, thereby to adhere to an unshown polygon-mirror, hard-disk, optical disk or the like mounted thereon.
As stated above, since the hub 107 tightly contacts the first rotation body 106 that is pressure-fitted to one end (the upper end) of the rotation shaft 105, the oil 103 that has once leaked from the oil-impregnated sintered bearing 104 can easily reach the hub 107 via the first rotation body 106, which deteriorates leakage prevention that has to be exerted by the first rotation body 106.
Therefore, there has been desired a motor in which even when lubricant that has leaked from a bearing reaches an oil deflector provided to oppose a hub, the oil is prevented from reaching the hub, which is assuredly able to prevent lubricant leakage.